BackgroundThe present study investigates the intrafractional accuracy of a frameless thermoplastic mask used for head immobilization during stereotactic radiotherapy. Non-invasive masks cannot completely prohibit head movements. Previous studies attempted to estimate the magnitude of intrafractional inaccuracy by means of pre- and postfractional measurements only. However, this might not be sufficient to accurately map also intrafractional head movements.Materials and methodsIntrafractional deviation of mask-fixed head positions was measured in five patients during a total of 94 fractions by means of close-meshed repeated ExacTrac measurements (every 1.4 min) conducted during the entire treatment session. A median of six (range: 4 to 11) measurements were recorded per fraction, delivering a dataset of 453 measurements.ResultsRandom errors (SD) for the x, y and z axes were 0.27 mm, 0.29 mm and 0.29 mm, respectively. Median 3D deviation was 0.29 mm. Of all 3D intrafractional motions, 5.5 and 0.4% exceeded 1 mm and 2 mm, respectively. A moderate correlation between treatment duration and mean 3D displacement was determined (rs = 0.45). Mean 3D deviation increased from 0.21 mm (SD = 0.26 mm) in the first 2 min to a maximum of 0.53 mm (SD = 0.31 mm) after 10 min of treatment time.ConclusionPre- and post-treatment measurement is not sufficient to adequately determine the range of intrafractional head motion. Thermoplastic masks provide both reliable interfractional and intrafractional immobilization for image-guided stereotactic hypofractionated radiotherapy. Greater positioning accuracy may be obtained by reducing treatment duration (< 6 min) and applying intrafractional correction.Trial registrationClinicaltrials.gov, NCT03896555, Registered 01 April 2019 - retrospectively registered.
Although some improvements have been made in recent years, the prognosis of pancreatic ductal adenocarcinoma remains poor. Surgical resection followed by adjuvant systemic therapy is the only curative treatment option in early stage disease. The role of radiotherapy in the treatment of pancreatic cancer is not well defined and still controversially discussed. Following the results of the ESPAC-1 trial, adjuvant radiochemotherapy (RCT) was no longer employed in most European countries. Nevertheless, in high-risk situations for local recurrence, the addition of adjuvant radiochemotherapy to adjuvant systemic therapy should be discussed, as it may lead to prolonged local tumor control. In resectable tumors, neoadjuvant radiochemotherapy or stereotactic body radiation therapy combined with systemic therapy showed encouraging results in phase I/II trials without increasing postoperative morbidity. Until the results of prospective randomized trials are available, neoadjuvant therapy in resectable pancreatic cancer is only recommended in clinical trials. In borderline resectable and locally advanced tumors, the addition of radiochemotherapy to systemic therapy leads to improved tumor response, and 20-30% of locally advanced tumors can be resected after neoadjuvant therapy. In locally advanced tumors with stable disease after systemic therapy, the addition of radiochemotherapy should be discussed to increase local control and prolong time to local progression. Modern radiotherapy with image guidance, intensitymodulated radiotherapy, and stereotactic body radiotherapy offer new perspectives for the future and will
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